The revision of the SOLAS convention in 2009 has demanded that a passenger ship ensures a required restoring force and navigates to a port by herself, even in a case where the ship is flooded or a fire breaks out due to damage to the ship.
For example, PTL 1 discloses a configuration which improves restoring ability as follows. The center of gravity of the ship is lowered by allowing water entering the inside of a ship body at the time of damage to flow into a space disposed in a bottom portion of the ship body.